1. Field of the Invention
This invention relates to a device for determining the push/pull capability of a human subject and, more specifically, to such a device which allows the subject to selectively move a push/pull bar mounted above the fixed walking surface.
2. Description of the Prior Art
Lower back pain is one of the most common causes of disability affecting society. Statistics indicate that in the United States, back pain is second only to the common cold as a leading cause of visits to a physician. Approximately eighty percent of people in industrial countries will experience some form of lower back pain in their life.
The annual incidents of lower back pain among industrial workers has been estimated at fifty per one thousand workers with a resulting loss of days at work which range from fourteen hundred per one thousand workers in the United States to about twenty-six hundred per one thousand workers in Great Britian. Further, research indicates that, in the United States alone, over ten million people are currently undergoing treatment for lower back pain and that one-fourth to one-half of the patients in physical therapy clinics are victims of lower back pain.
Additional statistics indicate that back pain is a self-limiting phenomenon with eighty to ninety percent of lower back pain patients tending to recover within six weeks regardless of the treatment prescribed. Within three months after a back injury, ninety-five percent of such patients will have recovered. Although it has been demonstrated that the incidents of lower back pain in non-industrial countries are similar to those in industrial countries, those in non-industrial countries do not appear to treat lower back pain as a disabling injury. In a modern society with advanced medical and legal systems, back pain has been elevated from a common ailment of unknown origin to some form of disabling injury. Further, increased reliance on injury compensation has given rise to the development of the "disability syndrome". In a recent evaluation of the Workers' Compensation Board for New York state in 1982, it has been reported that ninety-one percent of claimants represented by legal counsel were not working while seventy-seven percent of those not so represented were working. As a result, trauma to the back has grown into a broad and fertile field which lends itself to exaggeration and simulation of disability. Probably, in no other part of the body is the physician or examiner called upon so often to distinguish between real and simulated disability while having so few facts with which to make such an assessment.
Back problems clearly cost billions of dollars in treatment, compensation, lost wages and lost productivity. As a result, there is a need for a comprehensive evaluation and management program in the area of spinal disorders.
Basically, to evaluate the capability of a human subject to produce a force, three types of tests have been utilized. The three types of testing include isometric testing, isotonic testing and iso-kinetic testing. Isometric testing includes the measurement of a force produced without joint or body movement and may include, for example, the force generated while trying to lift or push an immovable object. Isotonic testing includes an evaluation of the force needed to move against a constant resistance but at a variable speed, such as with weight-lifting. Isokinetic testing includes the determination of the force generated on an object at a constant speed but with a variable resistance, such as with a water exercise dynamometer resistance. A dynamometer is a device which is well known in the testing and evaluating field. A dynamometer is a hydraulic or electro-magnetic device connected to a load cell and a computer to read force exerted during some type of activity pattern. A load cell is a pressure-sensitive device connected to a computer to record force, such as lifting, pushing or pulling, etc. The load source is quite often an integral part of a computerized dynamometer or other isometric testing device used in the prior art. Some dynamometers are primarily configured for testing rotary motion around a specific axis, such as an elbow, knee, or the like. However, other dynamometers can be configured for linear motion testing which includes motion in a specific plane, whether vertical or horizontal. Although a number of measuring and evaluating devices exist which can be utilized to help determine if a subject is able to push or pull an object under some conditions, the overall configuration and method employed are critical if the information obtained is to be pertinent and reliable for the evaluation of back problems. Although a number of such devices and methods have been proposed, they appear to include numerous disadvantages and limitations for a proper analysis of back problems.
A number of simplistic devices have been utilized to measure the horizontal pushing or pulling force exerted on a fixed wall or force plate by a subject. Clearly, such isometric testing is of limited value in the "real world" since one is seldom expected in industry to attempt to move an immovable object.
In an attempt to provide some type of testing more related to the "real world", other tests have been proposed which attempt to analyze the force required in various specific professions. For example, to analyze the back problems of cabin attendants in airplanes, a test was devised which used a strain gauge tensiometer to measure the force required to initiate motion of a standard aircraft cart. However, such force measurements still tend to be isometric. A similar test involved trolly carts which were attached to a strain gauge tensiometer to again produce the same type of isometric testing results.
In this regard, one commercially available device called "The Sled" produced by American Therapeutics, Inc. of Macon, Ga., would appear, at first analysis, to provide some "real world" means for evaluating the capability of a human subject to push or pull an object. However, "The Sled" device is a platform with handles on two sides and runners attached to the bottom. Weights are placed on the floor of the surface of the base to increase the load or force required for pushing or pulling. Although such a device may be used for rehabilitation purposes, it should be clear that it is of limited value for accurately and repeatedly testing subjects having back problems. For example, there is no means provided to insure medial or lateral stability during use. Further, the subject can actually see the amount of weight being moved. Finally, the force required to move such a device would clearly depend upon the floor surface. A wide range of coefficients of friction for carpeted or smooth surfaces would prevent the test results from being truly reliable or reproducible in other locations or for other human subjects.
One prior art design included in a report on the study and evaluation of back problems utilized a treadmill for testing. The treadmill would not be subject to different coefficients of friction like "The Sled". The test subject was directed to walk on the treadmill at a self-determined pace or speed while pushing or pulling a support bar fixedly mounted at the head of the treadmill. Measurement of the force was through the stationary support bar. However, the measurement method was derived from a variable speed and a variable resistance which were not true isotonic or isokinetic force measurements. The system appeared to measure some type of contracted or modified isometric measurements rather than either isotonic or isokinetic measurements.
Other testing systems are directed to the measurement of the pushing or pulling capability of a subject through the use of a wall mounted modified friction clutch mechanism or a dynamometer. For these systems, the test subject either holds onto a bar or handle or has a harness attached to the body. The subject then exerts a pushing or pulling force against the measuring device. With such a system, it would be possible for the subject to use body weight as the sole force producer by leaning against the handle or harness and without actually performing any pushing or pulling action. Further, such a system does not accurately provide an assessment of true push/pull strength due to the lack of proper stability. As a result, the results would not allow reasonable testing and re-testing comparisons for a complete analysis of present and future capabilities.
A number of patents have issued regarding the functional capabilities of human subjects, but these patents are usually directed to systems or devices which are not directed to the ability of the subject to push or pull an object while walking. Russian Pat. No. 640,745 and U.S. Pat. Nos. 3,988,931; 4,452,447; and 4,650,183 are directed to leg, ankle or foot joint exercising or measuring devices. U.S. Pat. No. 3,465,592 discloses an isokinetic exercise process and apparatus for evaluating the ability of the subject to rotate around various body joints.
A muscle testing apparatus of U.S. Pat. No. 3,922,918 tests the ability to lift a weight in a standing position while the exercise apparatus of U.S. Pat. No. 4,050,310 is directed to the lifting or pulling motion in a lying position. Exercising and/or evaluating apparatus when the subject is in a seated position is disclosed in U.S. Pat. Nos. 3,323,366 and 4,582,318.
U.S. Pat. No. 4,529,194 discloses an exercise machine which simulates the motion of cross-country skiing. Russian Pat. No. 216,991 discloses a device for determining the horizontal pressure exerted by a standing worker who is operating a mechanical device.
These patents are incorporated by reference as if included in their entirety herein. However, it should be recognized that the more sophisticated systems which may rely on various types of isometric, isotonic or isokinetic forces are directed to the exercise or evaluation of various joints or moving portions of the body.
Generally, it appears that none of the prior art devices discussed above include an adequate push/pull assessment device for a walking subject to properly determine the functional status, the disability assessment or the capability of the subject which would suggest whether or not the subject may return to work and, if so, under what conditions.